Fluoxetine exerts anti-inflammatory effects on human epidermal keratinocytes and suppresses their endothelin release

Fluoxetine is a safe antidepressant with remarkable anti-inflammatory actions; therefore, we aimed to investigate its effects on immortalized (HaCaT) as well as primary human epidermal keratinocytes in a polyinosinic-polycytidylic acid (p(I:C))-induced inflammatory model. We found that a non-cytotoxic concentration (MTT-assay, CyQUANT-assay) of fluoxetine significantly suppressed p(I:C)-induced expression and release of several pro-inflammatory cytokines (Q-PCR, cytokine array, ELISA), and it decreased the release of the itch mediator endothelins (ELISA). These effects were not mediated by the inhibition of the NF-κB or p38 MAPK pathways (western blot), or by the suppression of the p(I:C)-induced elevation of mitochondrial ROS production (MitoSOX Red labeling). Instead, unbiased activity profiling revealed that they were most likely mediated via the inhibition of the phosphoinositide 3-kinase (PI3K) pathway. Importantly, the PI3K-inhibitor GDC0941 fully mimicked the effects of fluoxetine (Q-PCR, ELISA). Although fluoxetine was able to occupy the binding site of GDC0941 (in silico molecular docking), and exerted direct inhibitory effect on PI3K (cell-free PI3K activity assay), it exhibited much lower potency and efficacy as compared to GDC0941. Finally, RNA-Seq analysis revealed that fluoxetine deeply influenced the transcriptional alterations induced by p(I:C)-treatment, and exerted an overall anti-inflammatory activity. Collectively, our findings demonstrate that fluoxetine exerts potent anti-inflammatory effects, and suppresses the release of the endogenous itch mediator endothelins in human keratinocytes, most likely via interfering with the PI3K pathway. Thus, clinical studies are encouraged to explore whether the currently reported beneficial effects translate in vivo following its topical administration in inflammatory and pruritic dermatoses.

TRPV4 Activation Increases the Expression of CD207 (Langerin) of Monocyte-Derived Langerhans Cells without Affecting their Maturation

Langerhans cells (LCs) are the sole professional antigen-presenting cell normally found in the human epidermal compartment. Research into their physiological role is hindered by the fact that they are invariably activated during isolation from the skin. To overcome this challenge, we turned to a monocyte-derived LC (moLC) model, which we characterized with RNA sequencing, and compared the transcriptome of moLCs with that of donor-matched immature dendritic cells. We found that moLCs express markers characteristic of LC2 cells as well as TRPV4. TRPV4 is especially important in the skin because it has been linked to the conservation of the skin barrier, immunological responses, as well as acute and chronic itch, but we know little about its function on LCs. Our results show that TRPV4 activation increased the expression of Langerin and led to increased intracellular calcium concentration in moLCs. Regarding the functionality of moLCs, we found that TRPV4 agonism had a mitigating effect on their inflammatory responses because it decreased their cytokine production and T-cell activating capability. Because TRPV4 has emerged as a potential therapeutic target in dermatological conditions, it is important to highlight LCs as, to our knowledge, a previously unreported target of these therapies.

Opioidergic Signaling-A Neglected, Yet Potentially Important Player in Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin diseases, the prevalence of which is especially high among children. Although our understanding about its pathogenesis has substantially grown in recent years, and hence, several novel therapeutic targets have been successfully exploited in the management of the disease, we still lack curative treatments for it. Thus, there is an unmet societal demand to identify further details of its pathogenesis to thereby pave the way for novel therapeutic approaches with favorable side effect profiles. It is commonly accepted that dysfunction of the complex cutaneous barrier plays a central role in the development of AD; therefore, the signaling pathways involved in the regulation of this quite complex process are likely to be involved in the pathogenesis of the disease and can provide novel, promising, yet unexplored therapeutic targets. Thus, in the current review, we aim to summarize the available potentially AD-relevant data regarding one such signaling pathway, namely cutaneous opioidergic signaling.

Genotoxic effects of glycidyltrimethylammonium chloride

Evaluation of the genotoxicity of epoxides is best carried out on a case by case basis. Although glycidyltrimethylammonium chloride (GTAC) is widely used in several industrial applications, its genotoxicity is poorly documented. Therefore, we have evaluated GTAC in a battery of 4 in vitro short-term tests for genotoxicity. We report here that GTAC mediates the induction of base-pair substitutions in S. typhimurium, gene conversion in S. cerevisiae (D7), chromosomal aberrations in CHO cells and viral DNA amplification in Chinese hamster CO6O cells. In view of these results, it is advisable to consider GTAC a potential carcinogen.

In vivo studies in male mice on the mutagenic effects of inorganic arsenic

The ability of sodium meta-arsenite (NaAsO2) to produce genetic damage in vivo has been evaluated in mice by the micronucleus test on bone marrow cells and the dominant lethality and sperm abnormality assays on male germ cells. The dose-related linear increase of micronuclei observed in somatic cells together with the negative results obtained in reproductive cells suggest that NaAsO2, under the conditions of the present experiments, displays clastogenic properties in vivo in laboratory animals, but is unable to produce heritable damage.

Lack of mutagenic activity of dimethylformamide

Different test systems have been utilized to evaluate the mutagenic and carcinogenic properties of dimethylformamide (DMF), an aliphatic amide used as a solvent in chemical industry. The Ames test was performed on different strains of Salmonella typhimurium, whereas the ability of DMF to induce structural aberrations in eukaryotic chromosomes was tested by in vitro observations on human lymphocytes and in vivo experiments on mouse bone marrow. Furthermore, male mice were treated with DMF for the induction of sperm abnormalities. The negative results obtained in all test systems as well as the absence of positive reports in man or in experimental animals with respect to induction of cancers suggest strongly that DMF is devoid of mutagenic or carcinogenic properties.